I have to say, you really should go visit either of Disney's water parks. They are truly a step beyond any other water park I've been to in terms of theming and environment. Again, much like the comparison with theme parks, there are other parks out there that might be bigger, or have crazier slides, etc., but as a total package Blizzard Beach and Typhoon Lagoon are top notch. They were built at a time when Disney seemed to spare no expense in terms of building great, unique environments and it shows. And until the cost cutting of hours this year (and the potential cutting of the shark lagoon), for the most park they have not suffered the cutbacks and service reductions the theme parks have (sort of forgotten by Burbank, I suppose).
Anyway, I know for us, who stay both on and off property, water parks definitely add a day to our trip. I agree, however, that the transportation changes have been horrible, to the point that next time we stay on property, we are never going to depend on Disney transport again and rent a car.